A conventional fan coupling device of the aforementioned type comprises a driving disc which is secured to a rotating shaft body, and an idle oil basin chamber which has a hollow inner core. Furthermore, on outer periphery wall portion of said idle oil chamber, there is a small diameter hole leading to a torque transfer chamber having a certain diameter hole through which the amount of oil supply can be controlled so that it will be less than the amount of oil exhausting from a dam member disposed at inner periphery wall portion of the oil on the side of the closed housing where oil can be stored. As a result, by controlling the "accompanying rotation" of the fan for the engine starting with an aid of the existence of said small diameter hole, a rapid increase of rotation can be prevented, abnormal fan noise can be reduced as well, in addition to the warm-up operation that can furthermore be promoted.
Although the above prior arts achieve these purposes to some extent, are they neither sufficient nor they are satisfactory. Particularly, the conventional type of the fan coupling device has been known to have a trend that does not control properly the "accompanying rotation" for a short period of time immediately after the engine starts while the operation condition under the repeated low revolution is shifted to the high rotation stage.
It is, therefore, an object of the present invention to provide a temperature sensitive fluid-type fan coupling device with which the "accompanying rotation" of the fan which momentarily stops while holding a large amount of oil inside the torque transfer chamber as a result of the aforementioned conventional technology, can be controlled for a short period of time immediately after the engine starting so that reduction of the fan noise can be achieved and warm-up operation in the winter or cold season can be promoted which improves upon and avoids the drawbacks of the fan coupling device of the prior art.
It is a more specific object of this invention to provide a temperature sensitive fluid-type fan coupling device with which the "accompanying rotation" phenomenon of the fan when the low rotation operation is rapidly shifted to a high revolution stage can be extremely effectively controlled, since the amount of enclosed oil can be significantly reduced to be of a regulated quantity.
It is another object of this invention to provide a temperature sensitive fluid-type fan coupling device with which the oil temperature can be effectively transferred outside through a heat transmission effect of a radial wall to promote a heat radiation effect.